JP2009003122A - Imaging device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform further accurate focus detection by improving the detection capability of luminance distribution of a subject in a focus detection part. <P>SOLUTION: The imaging device comprises an imaging element 107, a composition means 902, a connection means 903, and an arithmetic means 904. The imaging element 107 includes a plurality of focus detection parts 901 each composed of a pupil-divided first focus detection pixel 901a and a second focus detection pixel 901b, and the composition means 902 performs, in a plurality of sections CST assigned to the imaging element 107, processing for obtaining a first composition signal by composing an output signal from the first focus detection pixel 901a and processing for obtaining a second composition signal by composing output signal from the second focus detection pixel 901b. The connection means 903 performs processing for obtaining a first connection signal by connecting the first composition signal and processing for obtaining a second connection signal by connecting the second composition signal, and the arithmetic means 904 computes a focal slippage based on the first connection signal and the second connection signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus using an image pickup device capable of picking up at least one of a still image and a moving image with a plurality of two-dimensionally configured photoelectric conversion elements, and a control method thereof.

  There are a contrast detection method (called a blur method) and a phase difference detection method (called a shift method) as a general method using a light beam that has passed through a photographing optical system in an automatic focus detection / adjustment method of an imaging apparatus.

  The contrast detection method is a method often used in video movie equipment (camcorder) for video recording and electronic still cameras, and an image sensor is used as a focus detection sensor. Focusing on the output signal of the image sensor, particularly information on high-frequency components (contrast information), the position of the photographing optical system having the largest evaluation value is used as the in-focus position. However, it is necessary to move the photographic optical system while moving the photographic optical system by a small amount, and it is necessary to move until the evaluation value is found to be the maximum, so that it is possible to perform high-speed focus adjustment. Is not suitable.

  The other phase difference detection method is often used in a single-lens reflex camera using a silver salt film, and is the technology that has contributed most to the practical application of an auto focus (AF) single-lens reflex camera. In the phase difference detection method, the light beam that has passed through the exit pupil of the photographing optical system is divided into two, and the two divided light beams are received by a set of focus detection sensors. Then, the amount of deviation in the focus direction of the photographic optical system is directly obtained by detecting the amount of deviation of the output signal according to the amount of received light, that is, the amount of relative positional deviation in the beam splitting direction. Therefore, once the accumulation operation is performed by the focus detection sensor, the amount and direction of the focus shift can be obtained, and high-speed focus adjustment operation is possible. However, in order to divide the light beam that has passed through the exit pupil of the photographing optical system into two and obtain signals corresponding to the respective light beams, optical path dividing means such as a quick return mirror or a half mirror is provided in the imaging optical path, and beyond In general, a focus detection optical system and an AF sensor are provided. Therefore, there is a drawback that the apparatus is large and expensive.

  In order to eliminate this drawback, a technique for providing a phase difference detection function to an image sensor, making a dedicated AF sensor unnecessary, and realizing high-speed phase difference AF is also disclosed.

  For example, in Patent Document 1, in some of the light receiving elements (pixels) of the image sensor, the pupil division function is provided by decentering the sensitivity region of the light receiving unit with respect to the optical axis of the on-chip microlens. These pixels are used as focus detection pixels, and are arranged at predetermined intervals between the imaging pixel groups, thereby performing phase difference focus detection. Further, since the location where the focus detection pixels are arranged corresponds to a defective portion of the imaging pixel, image information is generated by interpolation from surrounding imaging pixel information.

  Moreover, in patent document 2, the pupil division function is provided by dividing the light receiving part of a part of pixels of the image sensor into two in the left-right direction or the up-down direction. These pixels are used as focus detection pixels (focus detection units), and are arranged at predetermined intervals between the imaging pixel groups to perform phase difference focus detection. Also, in this technology, since the image pickup pixel is missing at the position where the focus detection pixel is arranged, the image information is generated by interpolation from the peripheral image pickup pixel information.

  Further, in Patent Document 3, a pupil division function is provided by vertically dividing a light receiving portion of a part of a pixel of an image sensor in the vertical direction, and an output of the light receiving portion divided in two is individually processed. Phase difference focus detection is performed on a subject having a luminance distribution in the direction. In addition to adding the outputs of the two-part light receiving unit, it is also used for imaging signals, and by detecting the contrast between adjacent pixels in the left-right direction, contrast-type focus detection is performed on a subject having a luminance distribution in that direction. A technique for performing is disclosed.

Further, in Patent Document 4, a focus detection element obtained by dividing the light receiving unit in the left-right direction or the up-down direction is repeatedly arranged in every other row of the image sensor, so that an object having a luminance distribution in the left-right direction and the up-down direction can be obtained. On the other hand, a technique for performing phase difference type focus detection is disclosed.
JP 2000-156823 A JP 2000-292686 A JP 2001-305415 A JP 2003-153291 A

  However, in each of Patent Documents 1 to 4, the brightness of each focus detection unit is small, and the brightness distribution of the subject may not be sufficiently detected. Therefore, there is a problem that it is difficult to perform accurate focus detection.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve detection capability in a focus detection unit and perform more accurate focus detection.

  A first aspect of the present invention relates to an imaging apparatus, and includes an imaging element having a plurality of focus detection units each including a first focus detection pixel and a second focus detection pixel that are divided into pupils, In each of a plurality of sections allocated to the image sensor so as to include the focus detection unit, a process of obtaining a first synthesized signal by synthesizing an output signal from the first focus detection pixel; A synthesizing unit configured to synthesize an output signal from the second focus detection pixel to obtain a second synthesized signal; and a first unit configured by coupling the first synthesized signal across the plurality of sections. Based on the first connection signal and the second connection signal, the connection means for performing the process of obtaining the connection signal of the second and the second combined signal to obtain the second connection signal, And a calculation means for calculating the defocus amount of the imaging optical system. And wherein the Rukoto.

  According to a second aspect of the present invention, there is provided a control method for an image pickup apparatus including an image pickup device having a plurality of focus detection units each including a first focus detection pixel and a second focus detection pixel which are divided into pupils. In particular, a step of assigning a plurality of sections including the plurality of focus detection units to the image sensor, and a first synthesized signal obtained by synthesizing output signals from the first focus detection pixels in each of the plurality of sections. Obtaining a second synthesized signal by synthesizing an output signal from the second focus detection pixel in each of the plurality of sections, and obtaining the second synthesized signal over the plurality of sections. Concatenating synthesized signals to obtain a first concatenated signal; concatenating the second synthesized signal across the plurality of sections to obtain a second concatenated signal; and the first concatenated signal. And based on the second connection signal There are, characterized in that it comprises a step of calculating a defocus amount of the imaging optical system, the.

  ADVANTAGE OF THE INVENTION According to this invention, the detection capability in a focus detection part can be improved, and more exact focus detection can be performed.

  Hereinafter, an imaging device and a control method thereof according to preferred embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
1 to 20 are diagrams illustrating an imaging apparatus and a control method thereof according to an embodiment of the present invention. Hereinafter, the operation of the embodiment will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of an image pickup apparatus according to a preferred embodiment of the present invention, and shows an electronic camera in which a camera body having an image sensor and a photographing optical system are integrated. In the figure, reference numeral 101 denotes a first lens group disposed at the tip of a photographing optical system (imaging optical system), which is held so as to be able to advance and retract in the optical axis direction. Reference numeral 102 denotes an aperture / shutter which adjusts the light amount at the time of shooting by adjusting the aperture diameter, and also has a function as an exposure time adjustment shutter at the time of still image shooting. Reference numeral 103 denotes a second lens group. The diaphragm shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction, and perform a zooming function (zoom function) in conjunction with the forward and backward movement of the first lens group 101.

  Reference numeral 105 denotes a third lens group, which performs focus adjustment by moving back and forth in the optical axis direction. Reference numeral 106 denotes an optical low-pass filter, which is an optical element for reducing false colors and moire in a captured image. Reference numeral 107 denotes an image sensor composed of a CMOS image sensor and its peripheral circuits. This image sensor uses a two-dimensional single-plate color sensor in which a Bayer array primary color mosaic filter is formed on-chip on light receiving pixels of m pixels in the horizontal direction and n pixels in the vertical direction.

  Reference numeral 111 denotes a zoom actuator, which rotates a cam cylinder (not shown) to drive the first lens group 101 to the third lens group 103 forward and backward in the optical axis direction to perform a zooming operation. Reference numeral 112 denotes an aperture shutter actuator which controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light and controls the exposure time during still image photographing. Reference numeral 114 denotes a focus actuator, which performs focus adjustment by driving the third lens group 105 forward and backward in the optical axis direction.

  Reference numeral 115 denotes an electronic flash for illuminating a subject at the time of photographing, and a flash illumination device using a xenon tube is suitable, but an illumination device including an LED that emits light continuously may be used. Reference numeral 116 denotes an AF auxiliary light unit that projects an image of a mask having a predetermined aperture pattern onto a subject field via a light projection lens, thereby improving the focus detection capability for a dark subject or a low-contrast subject.

  Reference numeral 121 denotes a CPU which controls various controls of the camera body in the imaging apparatus. The CPU 121 includes, for example, a calculation unit, ROM, RAM, A / D converter, D / A converter, communication interface circuit, and the like. Then, the CPU 121 drives various circuits included in the imaging apparatus based on a predetermined program stored in the ROM, and executes a series of operations such as AF, shooting, image processing, and recording.

  An electronic flash control circuit 122 controls lighting of the illumination unit 115 in synchronization with the photographing operation. Reference numeral 123 denotes an auxiliary light driving circuit, which controls lighting of the AF auxiliary light unit 116 in synchronization with the focus detection operation. Reference numeral 124 denotes an image sensor drive circuit that controls the image capturing operation of the image sensor 107 and A / D-converts the acquired image signal and transmits it to the CPU 121. An image processing circuit 125 performs processing such as γ conversion, color interpolation, and JPEG compression of an image acquired by the image sensor 107.

  A focus driving circuit 126 controls the focus actuator 114 based on the focus detection result, and performs focus adjustment by driving the third lens group 105 back and forth in the optical axis direction. Reference numeral 128 denotes an aperture shutter drive circuit which controls the aperture shutter actuator 112 to control the aperture of the aperture / shutter 102. Reference numeral 129 denotes a zoom drive circuit that drives the zoom actuator 111 in accordance with the zoom operation of the photographer.

  Reference numeral 131 denotes a display such as an LCD, which displays information related to the shooting mode of the imaging apparatus, a preview image before shooting and a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. An operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. Reference numeral 133 denotes a detachable flash memory that records a photographed image.

  FIG. 2 is a schematic circuit diagram of an image sensor according to a preferred embodiment of the present invention, which can be manufactured by using the technique disclosed in Japanese Patent Laid-Open No. 09-046596 by the present inventor. . FIG. 2 shows a pixel region of 2 columns × 4 rows in an area sensor in which CMOS image sensors are two-dimensionally arranged. When used as an image sensor, a plurality of pixel regions shown in FIG. 2 are arranged to enable acquisition of a high resolution image. In the present embodiment, an image sensor for a digital still camera having a pixel pitch of 2 μm, an effective pixel number of 3000 columns × 2000 rows = 6 million pixels, and an image capture screen size of 6 mm × 4 mm is described as an example. .

In FIG. 2, reference numeral 1 denotes a photoelectric conversion element formed of a transistor, 2 denotes a photogate, and 3 denotes a transfer switch transistor. The photoelectric conversion element 1, the photogate 2, and the transfer switch transistor 3 constitute one pixel among the pixels 30-11 to 30-32. 4 is a reset transistor, 5 is a source follower amplifier transistor, 6 is a horizontal selection switch transistor, and 7 is a load transistor of the source follower. 8 the dark output transfer transistor 9 bright output transfer transistor 10 is dark output accumulation capacitor _C TN, 11 is bright output accumulation capacitor _C TS, 12 a horizontal transfer transistor. 13 is a horizontal output line reset transistor, 14 is a differential output amplifier, 15 is a horizontal scanning circuit, and 16 is a vertical scanning circuit. Note that each transistor shown in FIG. 2 can be formed of, for example, a MOS transistor.

FIG. 3 shows a cross-sectional view of a unit composed of two pixels. The unit 301 in FIG. 3 shows an example in which two pixels of the pixel 30-11 and the pixel 30-21 in FIG. 2 are configured as one unit. In FIG. 3, 17 is a P well, 18 is a gate insulating film formed of an oxide film, 19 is a first layer of poly-Si, 20 is a second layer of poly-Si, and 21 is an n ⁺ floating diffusion portion (FD). is there. The FD 21 is connected to another photoelectric conversion element via another transfer transistor. In FIG. 3, the drains of the two transfer switch transistors 3 and the FD portion 21 are made common to improve the sensitivity by miniaturization and the capacitance reduction of the FD portion 21, but the FD portion 21 is connected by a wiring such as Al. Also good.

  Next, the operation will be described with reference to the timing chart of FIG. This timing chart is for the case of all pixel independent output. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the signal waveform of each signal.

  First, according to the timing output from the vertical scanning circuit 16, the control pulse φL is set to high to reset the vertical output line. Further, the control pulses φR0, φPG00, and φPGe0 are set high, the reset transistor 4 is turned on, and the first-layer poly Si 19 of the photogate 2 is set high. In the period T0, the control pulse φS0 is set high, the selection switch transistor 6 is turned on, and the pixels on the first and second lines are selected. Next, the control pulse φR0 is set low, the reset of the FD unit 21 is stopped, and the FD unit 21 is set in a floating state. The charge accumulated in the FD unit 21 is read from the source as a voltage change via the gate of the source follower amplifier transistor 5. Thereafter, the control pulse φTN is set to high in the period T1, and the dark voltage read from the FD unit 21 is output to the storage capacitor CTN10 by the source follower operation.

  Next, in order to perform photoelectric conversion output of the pixels of the first line, the control pulse φTX00 of the first line is set high, the transfer switch transistor 3 is turned on, and then the control pulse φPG00 is set low during the period T2. At this time, a voltage relationship is preferable in which the potential well that has spread under the photogate 2 is raised so that photogenerated carriers are completely transferred to the FD portion 21. Therefore, if complete transfer is possible, the control pulse φTX may be a fixed potential instead of a pulse.

  In the period T2, the electric charge from the photoelectric conversion element 1 of the photodiode is transferred to the FD unit 21, so that the potential of the FD unit 21 changes according to light. At this time, since the source follower amplifier transistor 5 is in a floating state, the potential of the FD section 21 is output to the storage capacitor CTS11 with the control pulse φTs being high in the period T3. At this time, the dark output and the light output of the pixels on the first line are stored in the storage capacitors CTN10 and CTS11, respectively. In the period T4, the control pulse φHC is temporarily set to high to turn on the horizontal output line reset transistor 13 to reset the horizontal output line, and in the horizontal transfer period, the dark output of the pixel to the horizontal output line is performed by the scanning timing signal of the horizontal scanning circuit 15. And output light. At this time, if the differential output VOUT is obtained by the differential amplifier 14 of the storage capacitors CTN10 and CTS11, a signal with good S / N from which random noise and fixed pattern noise of the pixel are removed can be obtained. The photocharges of the pixels 30-12 and 30-22 are accumulated in the respective storage capacitors CTN10 and CTS11 simultaneously with the pixels 30-11 and 30-21. However, in the readout, the timing pulse from the horizontal scanning circuit 15 is delayed by one pixel, read out to the horizontal output line, and output from the differential amplifier 14.

  In the present embodiment, the configuration in which the differential output VOUT is performed in the chip is shown. However, the same effect can be obtained even if a conventional CDS (Correlated Double Sampling) circuit is used outside without being included in the chip. Is obtained.

  After outputting a bright output to the storage capacitor CTS11, the control transistor φR0 is set to high to turn on the reset transistor 4, and the FD unit 21 is reset to the power supply VDD. After the horizontal transfer of the first line is completed, the second line is read. In reading the second line, the control pulse φTXe0 and the control pulse φPGe0 are driven in the same manner, and high pulses are supplied to the control pulses φTN and φTS, respectively, and photocharges are accumulated in the storage capacitors CTN10 and CTS11, respectively. Take the output. With the above driving, the first and second lines can be read independently. Thereafter, by scanning the vertical scanning circuit and similarly reading out the 2n + 1 line and the 2n + 2 line (n = 1, 2,...), All pixels can be independently output. For example, when n = 1, first, the control pulse φS1 is set to high, and then φR1 is set to low. Next, the control pulses φTN and φTX01 are set to high, the control pulse φPG01 is set to low, the control pulse φTS is set to high, and the control pulse φHC is set to high temporarily to read the pixel signals of the pixels 30-31 and 30-32. Subsequently, the control pulses φTXe1, φPGe1 and the control pulse are applied in the same manner as described above, and the pixel signals of the pixels 30-41, 30-42 are read out.

  5 to 7 are diagrams illustrating the structures of the imaging pixels and the focus detection pixels. In a preferred embodiment of the present invention, out of 4 pixels of 2 rows × 2 columns, a pixel having a spectral sensitivity of G (green) is arranged in 2 diagonal pixels, and R (red) is placed in the other 2 pixels. A Bayer arrangement in which one pixel each having B (blue) spectral sensitivity is arranged is employed. In addition, focus detection pixels having a structure described later are distributed and arranged in a predetermined rule between the Bayer arrays.

  FIG. 5 shows the arrangement and structure of the imaging pixels. FIG. 5A is a plan view of 2 × 2 imaging pixels. As is well known, in the Bayer array, G pixels are arranged diagonally, and R and B pixels are arranged in the other two pixels. A structure of 2 rows × 2 columns is repeatedly arranged.

FIG. 5B is a cross-sectional view taken along the line AA in FIG. ML denotes an on-chip microlens arranged in front of each pixel, CF _R is a color filter, CF _G of R (red), a G (green) color filter. PD (Photo Diode) schematically shows the photoelectric conversion element of the CMOS image sensor described in FIG. CL (Contact Layer) is a wiring layer for forming signal lines for transmitting various signals in the CMOS image sensor. TL schematically shows the photographing optical system.

  Here, the on-chip microlens ML and the photoelectric conversion element PD of the imaging pixel are configured to capture the light beam that has passed through the photographing optical system TL (Taking Lens) as effectively as possible. In other words, the exit pupil EP (Exit Pupil) of the photographing optical system TL and the photoelectric conversion element PD are in a conjugate relationship by the microlens ML, and the effective area of the photoelectric conversion element is designed to be large. Further, FIG. 5B describes the incident light beam of the R pixel, but the G pixel and the B (blue) pixel have the same structure. Therefore, the exit pupil EP corresponding to each RGB pixel for imaging has a large diameter, and the S / N of the image signal is improved by efficiently taking in the light flux (photon) from the subject.

FIG. 6 shows the arrangement and structure of focus detection pixels for performing pupil division in the horizontal direction (lateral direction) of the photographing optical system. Here, the horizontal direction or the horizontal direction is perpendicular to the optical axis and extends in the horizontal direction when the imaging apparatus is set so that the optical axis of the imaging optical system and the long side of the imaging screen are parallel to the ground. The direction along a straight line. Further, the pupil division direction in FIG. 6 is the horizontal direction. FIG. 6A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When obtaining an image signal for recording or viewing, the main component of luminance information is acquired by G pixels. Since human image recognition characteristics are sensitive to luminance information, image quality degradation is easily recognized when G pixels are lost. On the other hand, the R pixel or the B pixel is a pixel that acquires color information (color difference information). However, since human visual characteristics are insensitive to color information, the pixel that acquires color information has some defects. However, image quality degradation is difficult to recognize. Therefore, in the present embodiment, among the pixels of 2 rows × 2 columns, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are replaced with focus detection pixels. The focus detection pixels are denoted as S _HA and S _HB in FIG.

FIG. 6B is a cross-sectional view taken along the line AA in FIG. The microlens ML and the photoelectric conversion element PD have the same structure as the imaging pixel shown in FIG. In this embodiment, since the signal of the focus detection pixel is not used for image generation, a transparent film CF _W (white) is disposed instead of the color separation color filter. Moreover, since pupil division is performed by the image sensor, the opening of the wiring layer CL is biased in one direction with respect to the center line of the microlens ML. Specifically, since the opening OP _HA of the pixel S _HA and the opening OP _HA are biased to the right side, the light beam that has passed through the left exit pupil EP _HA of the photographing optical system TL is received. Similarly, since the opening OP _HB of the pixel S _HB is biased to the left side, the light beam that has passed through the right exit pupil EP _HB of the imaging optical system TL is received. Therefore, the pixels _SHA are regularly arranged in the horizontal direction, and the subject image acquired by these pixel groups is defined as an A image. Further, the pixels SH _B are also regularly arranged in the horizontal direction, and the subject image acquired by these pixel groups is a B image. By detecting the relative positions of the A image and the B image, the amount of focus deviation of the subject image is detected. (Defocus amount) can be detected.

In the pixels S _HA and S _HB , focus detection is possible for an object having a luminance distribution in the horizontal direction of the shooting screen, for example, a vertical line, but focus detection is not possible for a horizontal line having a luminance distribution in the vertical direction. . Therefore, in the present embodiment, the latter can be configured to include pixels that perform pupil division in the vertical direction (longitudinal direction) of the photographing optical system so that the focus state can be detected.

FIG. 7 shows the arrangement and structure of focus detection pixels for performing pupil division in the vertical direction (vertical direction or vertical direction) of the photographing optical system. Here, the vertical direction, the vertical direction, and the vertical and horizontal directions are perpendicular to the optical axis when the imaging apparatus is set so that the optical axis of the imaging optical system and the long side of the imaging screen are parallel to the ground. A direction along an extending straight line. Further, the pupil division direction in FIG. 7 is the vertical direction. FIG. 7A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. As in FIG. 6A, G pixels are left as imaging pixels, and R pixels and B pixels are Are focus detection pixels. The focus detection pixels are denoted as S _VC and S _VD in FIG.

FIG. 7B is a cross-sectional view taken along the line AA in FIG. The pixel shown in FIG. 6B has a structure in which pupils are separated in the horizontal direction, whereas the pixel in FIG. 7B has a vertical pupil separation direction, but the other pixels have the same structure. is there. Since the opening OP _VC of the pixel S _VC is offset downward, and receives a light beam that has passed through an exit pupil EP _VC of the upper of the photographic optical system TL. Similarly, since the opening OP _VD of the pixel S _VD is biased upward, the light beam that has passed through the lower exit pupil EP _VD of the imaging optical system TL is received. Therefore, the pixels _SVC are regularly arranged in the vertical direction, and a subject image acquired by these pixel groups is defined as a C image. Further, the pixels _SVD are also regularly arranged in the vertical direction, and the subject image acquired by these pixel groups is defined as a D image. Then, by detecting the relative positions of the C image and the D image, it is possible to detect the focus shift amount (defocus amount) of the subject image having the luminance distribution in the vertical direction.

  FIG. 8 is a diagram schematically showing focus detection in a preferred embodiment of the present invention. The image sensor 107 includes a plurality of focus detection units 901 including first focus detection pixels 901a and second focus detection pixels 901b that are divided into pupils. The image sensor 107 also includes a plurality of imaging pixels for photoelectrically converting a subject image formed by a photographing optical system (imaging optical system). The CPU 121 includes a combining unit 902, a connecting unit 903, and a calculating unit 904. The CPU 121 also assigns a plurality of sections (regions) CST to the imaging surface of the imaging element 107 so as to include a plurality of focus detection units 901. The CPU 121 can appropriately change the size, arrangement, number, etc. of the section CST. The synthesizing unit 902 performs a process of synthesizing the output signals from the first focus detection pixels 901a to obtain a first synthesized signal of one pixel in each of the plurality of sections CST assigned to the image sensor 107. The synthesizing unit 902 also performs a process of synthesizing the output signals from the second focus detection pixels 901b in each section CST to obtain a second synthesized signal of one pixel. In the plurality of sections CST, the connecting unit 903 connects the pixels that are the first combined signal to obtain the first connected signal, and connects the second combined signal to obtain the second connected signal. Process. In this way, a connection signal in which the number of sections of pixels are connected to each of the first focus detection pixel 901a and the first focus detection pixel 901b is obtained. The computing means 904 computes the defocus amount of the imaging optical system based on the first connection signal and the second connection signal. In this way, since the output signals of the focus detection pixels in the same pupil division direction arranged in the section are synthesized, even if the brightness of each focus detection unit is small, the brightness distribution of the subject is Sufficient detection is possible. Further, as described later, the ability to capture an image of a fine line (high frequency pattern) is improved by arranging the focus detection units 901 densely in the pupil division direction (horizontal direction in FIG. 8). In FIG. 8, the case of dividing the pupil in the horizontal direction is shown as an example in order to simplify the explanation, but the same applies to the case of dividing the pupil in the vertical direction as described later.

  9 to 11 are diagrams for explaining the arrangement rules of the imaging pixels and focus detection pixels shown in FIGS. 5 to 7.

FIG. 9 is a diagram for explaining a minimum unit arrangement rule according to the preferred first embodiment of the present invention when focus detection pixels are discretely arranged between imaging pixels. In FIG. 9, a square area of 10 rows × 10 columns = 100 pixels is defined as one block. In the upper left block BLKh (1, 1), a pair of focus detection pixels (first focus detection unit) that divides the lower left R pixel and B pixel in the horizontal direction (first direction). _Replace with S _HA and S _HB .

In the block BLKv (1, 2) on the right side, a pair of focus detection pixels (second pixels) that similarly divide the lower left R pixel and B pixel in the vertical direction (second direction). Focus detection unit) _Replace with S _VC and S _VD . The pixel arrangement of the block BLKv (2, 1) adjacent below the first block BLKh (1, 1) is the same as that of the block BLKv (1, 2). The pixel arrangement of the block BLKh (2, 2) on the right side is the same as that of the leading block BLKh (1, 1).

  Generalizing this arrangement rule, in block BLK (i, j), if i + j is an even number, a horizontal pupil division focus detection pixel is arranged, and if i + j is an odd number, a vertical pupil division focus detection pixel is arranged. Will be placed. Then, a 2 × 2 = 4 block in FIG. 9, that is, an area of 20 rows × 20 columns = 400 pixels is defined as a cluster as an upper array unit of the block.

FIG. 10 is a diagram for explaining an arrangement rule with the above cluster as a unit. In FIG. 10, the upper left cluster composed of 20 rows × 20 columns = 400 pixels is assumed to be CST (u, w) = CST (1, 1). In the cluster CST (1, 1), the lower left R pixel and B pixel of each block are replaced with focus detection pixels S _HA and S _HB or S _VC and S _VD .

  In the cluster CST (1, 2) on the right side, the focus detection pixels in the block are arranged at positions shifted upward by two pixels with respect to the cluster CST (1, 1). In the cluster CST (2, 1) adjacent to the first cluster CST (1, 1), the focus detection pixel is arranged in the block in the right direction with respect to the cluster CST (1, 1). Arranged at a position shifted by two pixels. When the above rule is repeatedly applied, the arrangement shown in FIG. 10 is obtained.

  This arrangement rule is generalized as follows. Note that the coordinates of the focus detection pixels are defined by the coordinates of the upper left pixel of the four pixels including the G pixel shown in FIG. 6 or 7 as one unit (pair). In the coordinates in each block, the upper left is (1, 1), and the lower direction and the right direction are positive.

  When the above definition is applied, in the cluster CST (u, w), the horizontal coordinate of the focus detection pixel pair in each block is 2 × u−1, and the vertical coordinate is 11-2 × w. Then, 5 × 5 = 25 clusters in FIG. 10, that is, an area of 100 rows × 100 columns = 10,000 pixels is defined as a field as an upper array unit of the clusters.

  FIG. 11 is a diagram for explaining an arrangement rule with the above field as a unit. In the figure, the upper left field composed of 100 rows × 100 columns = 10,000 pixels is assumed to be FLD (q, r) = FLD (1,1). In this embodiment, all the fields FLD (q, r) are arranged in the same manner as the first field FLD (1, 1). Therefore, when 30 FLDs (1, 1) are arranged in the horizontal direction and 20 in the vertical direction, an imaging region of 3000 columns × 2000 rows = 6 million pixels is configured by 600 fields. The focus detection pixels can be uniformly distributed over the entire imaging region.

  Next, a group of pixels and a signal addition method at the time of focus detection will be described with reference to FIGS. FIG. 12 is a diagram for explaining a pixel grouping method in the case of performing focus detection in the lateral shift direction of a subject image formed by the photographing optical system. The focus detection in the lateral shift direction performs phase difference focus detection using the focus detection pixels for dividing the exit pupil of the photographing optical system in the horizontal direction (left-right direction, horizontal direction) described in FIG. Refers to that.

The pixel arrangement shown in FIG. 12 is the same as that described with reference to FIG. 10. In focus detection, a total of 10 blocks of 1 block in the horizontal direction and 10 blocks in the vertical direction are combined into one group (here Then, the first section is defined. In the present embodiment, as an example, one focus detection region is configured by 30 sections arranged in the horizontal direction. That is, an area of 100 rows × 300 columns = 30,000 pixels is one focus detection area. This one focus detection area is defined as an AF area. Here, in one section, five pixels S _HA that perform one pupil division in the horizontal direction and five pixels S _HB that perform the other pupil division are included. Therefore, in the present embodiment, the outputs of the five _SHAs are added to form a signal of one pixel, and one AF signal of one image signal (referred to as A image) for phase difference calculation is obtained. Similarly, the outputs of the five _SHBs are added to form a signal of one pixel, and 1AF pixel of the other image signal (referred to as B image) for phase difference calculation is obtained.

FIG. 13 is a diagram for explaining a subject image capturing capability in one section. FIG. 13A shows the section at the left end of FIG. A horizontal line PRJ _h shown at the lower end is a first projection line extending in a second direction orthogonal to the pupil division direction (first direction) of the focus detection pixels S _HA and S _HB. . Vertical line PRJ _v shown at the right end is a second projection axis which extends in the pupil division direction. Here, all the pixels S _HA in one section are added, and S _HB is also added. Accordingly, when one section is regarded as one AF pixel, pixels S _HA and S _HB alternate when a light receiving portion included in one AF pixel is projected onto a projection axis PRJ _h in a direction orthogonal to the pupil division direction. It can be seen that they are closely lined up. When the arrangement pitch of the pixels S _{HA on} the projection axis PRJ _h in the direction orthogonal to the pupil division direction at this time is P1, P1 = PH _h = 2 (unit is a pixel). When expressed by the spatial frequency F1 instead of the pitch, F1 = 0.5 (unit is pixel / pixel). Similarly, the arrangement pitch of the pixels S _HB on the projection axis PRJ _h is also P1 = 2 (unit is pixel), and F1 = 0.5 (unit is pixel / pixel) in the spatial frequency notation.

On the other hand, when projecting the light receiving portions included in one AF pixel projection axis PRJ _v in the pupil division direction, the pixels S _HA and S _HB is seen that aligned sparsely. If the arrangement pitch of the pixels S _{HA on} the projection axis PRJ _{v at} this time is P2, then P2 = PH _v = 20 (the unit is a pixel). When expressed by the spatial frequency F2 instead of the pitch, F2 = 0.05 (unit: pixel / pixel). Similarly, the array pitch of the pixels _{S HB} along the projection PRJ _v also, P2 = 20 (the unit is a pixel), a F2 = 0.05 (the unit is pixel / pixel) of the spatial frequency notation.

  That is, the AF pixels in the present embodiment have the same arrangement pitch in the pupil division direction and the direction orthogonal thereto with respect to the dispersion characteristics before grouping. However, the sampling error in the pupil division direction is reduced by making the group shape at the time of grouping rectangular. Specifically, the maximum dimension L1 in the direction orthogonal to the pupil division direction of one section is 10 pixels, and the maximum dimension L2 in the pupil division direction is 100 pixels. That is, by setting the section size to L1 <L2, the sampling frequency F1 in the direction orthogonal to the pupil division direction is set to a high frequency (fine), and the sampling frequency F2 in the pupil division direction is set to a low frequency (sparse).

FIG. 13B illustrates an image capturing capability when a thin line subject image is projected onto the AF pixel (one section) described with reference to FIG. In FIG. 13B, LINE _v represents a thin vertical line projected on the image sensor 107, the width of which is 4 pixels in terms of pixel, and the actual size of the image is 8 μm. At this time, in the section SCT _h (1), the focus detection pixels included in the block BLK (3, 1) and the block BLK (5, 1) capture the subject image. Note that the minimum size of the subject image is determined by the aberration of the photographing optical system and the characteristics of the optical LPF disposed on the front surface of the image pickup element. Accordingly, in one section of this embodiment, an image is captured by at least one pixel S _HA and S _HB at least, and no capture leakage occurs.

On the other hand, LINE _h in FIG. 13B represents a thin horizontal line projected on the image sensor 107, and the width thereof is 4 pixels in terms of pixel as in the above-described LINE _v, and the actual size of the image is 8 μm. Yes. At this time, the horizontal line LINE _h covers the block BLK (5, 1), but is not captured by the focus detection pixels S _HA and S _HB . However, the section SCT _h (1) is for performing focus detection on a subject having a luminance distribution in the horizontal direction such as a vertical line. Therefore, for an object having a luminance distribution in the vertical direction such as a horizontal line, an image capturing omission due to focus detection pixels may occur.

  FIG. 14 is a diagram for explaining a pixel grouping method in the case where focus detection in the direction of vertical shift of a subject image formed by a photographing optical system is performed. The focus detection in the longitudinal shift direction is a phase difference focus detection using the focus detection pixels for dividing the exit pupil of the photographing optical system in the vertical direction (vertical direction, that is, the vertical direction) described in FIG. To do. That is, it corresponds to the one obtained by rotating FIG. 12 by 90 degrees.

The pixel arrangement shown in FIG. 14 is the same as that described with reference to FIG. Then, the second section) is defined. In the present embodiment, as an example, one focus detection region is configured by 30 sections arranged in the vertical direction. That is, an area of 300 rows × 100 columns = 30,000 pixels is one focus detection area. This one focus detection area is also defined as an AF area as in FIG. Here, in one section, five pixels _SVC performing one pupil division in the vertical direction and five pixels _SVD performing the other pupil division are included. Therefore, in the present embodiment, the outputs of five _SVCs are added to form one AF pixel of one image signal (referred to as a C image) for phase difference calculation. Similarly, the outputs of the five _SVDs are added to form a 1AF pixel of the other image signal (referred to as a D image) for phase difference calculation.

FIG. 15 is a diagram for explaining the subject image capturing capability in one section, and is equivalent to the one obtained by rotating FIG. 13 by 90 degrees. FIG. 15A is a cut out section at the upper end of FIG. The vertical line PRJ _v shown at the right end, the third projection axis extending in a first direction perpendicular to the pupil division direction of the pixel S _VC and S _VD for focus detection (second direction), shown at the lower end The horizontal line PRJ _{h made} is the fourth projective axis extending in the pupil division direction. Also in FIG. 15A, all the pixels S _VC in one section are added, and SV _D is also added. Therefore, when one section is regarded as one AF pixel, pixels S _VC and S _VD are alternately arranged densely when the light receiving portion included in the one AF pixel is projected onto a projection axis PRJ _v in a direction orthogonal to the pupil division direction. I understand. If the arrangement pitch of the pixels S _{VC on} the projection axis PRJ _v in the direction orthogonal to the pupil division direction at this time is P1, P1 = PV _v = 2 (unit is pixel). When expressed by the spatial frequency F1 instead of the pitch, F1 = 0.5 (unit is pixel / pixel). Similarly, the array pitch of the pixels _{S VD} along the projection PRJ _v be P1 = 2 (the unit is a pixel), the F1 = 0.5 (the unit is a pixel / pixel) of the spatial frequency notation.

On the other hand, when projecting the light receiving portions included in one AF pixel projection axis PRJ _h in the pupil division direction, the pixels S _VC and SV _D it can be seen that aligned sparsely. When the arrangement pitch of the pixels S _{VC on} the projection axis PRJ _{h at} this time is P2, P2 = PV _h = 20 (unit is pixel). When expressed by the spatial frequency F2 instead of the pitch, F2 = 0.05 (unit: pixel / pixel). Similarly, the array pitch of the pixels _{S VD} along the projection PRJ _v also, P2 = 20 (the unit is a pixel), a F2 = 0.05 (the unit is pixel / pixel) of the spatial frequency notation.

  As described above, the sampling characteristics of the AF pixels in FIG. 15 are the same as those in FIG. 13, that is, F1> F2 when the pupil division direction is taken as a reference. This is because also in the section of FIG. 15, the section dimension L1 in the direction orthogonal to the pupil division direction and the dimension L2 in the pupil division direction are set to L1 <L2. Accordingly, it is possible to accurately detect luminance information in a direction orthogonal to the pupil division direction even for a subject having a high spatial frequency, and the S / N of the focus detection signal can be obtained by adding a plurality of pixels even if the subject luminance is low. The ratio can be improved.

FIG. 15B illustrates an image capturing capability when a thin line subject image is projected onto the AF pixel (one section) described with reference to FIG. In FIG. 15B, LINE _h represents a thin horizontal line projected on the image sensor 107, the width of which is 4 pixels in terms of pixel, and the actual size of the image is 8 μm. At this time, in the section SCT _v (1), the focus detection pixels included in the block BLK (1, 4) and the block BLK (1, 6) capture the subject image.

On the other hand, LINE _v in FIG. 15B represents a thin vertical line projected on the image sensor 107, and the width thereof is 4 pixels in terms of pixel as in the above-described LINE _h, and the actual size of the image is 8 μm. ing. At this time, the vertical line LINE _v covers the block BLK (1, 6), but is not captured by the focus detection pixels S _VC and S _VD . However, the section SCT _v (1) is for performing focus detection on a subject having a luminance distribution in the vertical direction, such as a horizontal line. Therefore, for an object having a luminance distribution in the horizontal direction such as a vertical line, an omission of image capture by the focus detection pixels may occur.

  FIG. 16 is a diagram conceptually illustrating the pupil division function of the image sensor according to the first embodiment. TL is a photographing optical system, 107 is an image sensor, OBJ is a subject, and IMG is a subject image.

As described with reference to FIG. 5, the imaging pixel receives the light beam that has passed through the entire exit pupil EP of the imaging optical system. On the other hand, the focus detection pixel has a pupil division function as described with reference to FIGS. Specifically, the pixel S _HA in FIG. 6 is a light beam LHA having passed through the pupil of the left looking at the lens rear from the imaging surface, i.e. receives a light flux that has passed through the pupil EPHA in FIG. 16. Similarly, the pixels S _HB , S _VC and S _VD receive light beams LHB, LHC and LHD that have passed through the pupils EPHB, EPVC and EPVD, respectively. Since the focus detection pixels are distributed over the entire area of the image sensor 107 as described with reference to FIG. 11, focus detection is also possible over the entire image pickup area.

FIG. 17 is a diagram for explaining an image acquired during focus detection and a focus detection area. In FIG. 17, the subject image formed on the imaging surface includes a person at the center, a close-up tree on the left side, and a distant mountain range on the right side. In the present embodiment, the focus detection pixels include the lateral displacement detection pixel pairs S _HA and S _HB and the longitudinal displacement detection pixel pairs S _VC and S _VD as shown in FIG. Are arranged at an even density. At the time of lateral shift detection, AF pixel signals for phase difference calculation are grouped as shown in FIGS. Further, when detecting vertical shift, AF pixel signals for phase difference calculation are grouped as shown in FIGS. Therefore, it is possible to set a distance measurement area for detecting lateral deviation and longitudinal deviation at an arbitrary position in the imaging area.

In FIG. 17, a human face exists in the center of the screen. Therefore, when the presence of a face is detected by a known face recognition technique, a focus detection area AFAR _h (x1, y1) for detecting lateral deviation centered on the face area and a focus detection area AFAR _v (for detecting vertical deviation). x3, y3) are set. Here, the subscript h represents the horizontal direction, and (x1, y1) and (x3, y3) represent the coordinates of the upper left corner of the focus detection area. Then, the A image signal of each adds five focus detection pixels for S _HA included in a section, a phase difference detection linked across this 30 section of the focus detection area AFAR h _(x1, y1) AFSIG _h (A1). Similarly, adding the five focus detection pixels for S _HB of each section, B image signal for phase difference detection which is connected across this 30 section is AFSIG h _(B1). Then, by calculating the relative lateral shift amount between the A image signal AFSIG _h (A1) and the B image signal AFSIG _h (B1) by a known correlation calculation, the defocus amount (defocus amount) of the subject can be obtained. it can.

Focus detection area AFAR _v (x3, y3) obtains the defocus amount Similarly for. Then, the two defocus amounts detected in the lateral shift and vertical shift focus detection areas are compared, and a highly reliable value may be adopted.

On the other hand, since the trunk of the tree on the left side of the screen is mainly composed of vertical line components, that is, has a luminance distribution in the horizontal direction, it is determined that the subject is suitable for lateral shift detection, and the focus detection area AFAR _h ( x2, y2) are set. The ridgeline of the mountains on the right side of the screen, because the horizontal line component mainly has, namely, a luminance distribution in the longitudinal direction, it is determined that object suitable for longitudinal defocus detection, focus detection area AFAR _v for longitudinal defocus detection (X4, y4) is set.

  As described above, in the present embodiment, since the focus detection area for detecting the lateral shift and the vertical shift can be set at an arbitrary position on the screen, even if the projection position of the subject and the directionality of the luminance distribution are various, it is accurate. Focus detection is possible.

  18 to 20 are flowcharts for explaining control methods such as focus adjustment and imaging method of the imaging apparatus according to the preferred embodiment of the present invention. The control method of this flowchart can be similarly applied to the second to fourth embodiments described later. Note that each step of this flowchart is executed by the CPU 121 of FIG. 1 unless otherwise specified. Hereinafter, the control flow after FIG. 18 will be described with reference to FIGS. 1 to 17 described above.

  FIG. 18 is a main flow of the imaging apparatus according to the preferred embodiment of the present invention. When the photographer turns on the power switch of the imaging apparatus in step S101, the CPU 121 checks the operation of each actuator and imaging element in the imaging apparatus in step S103. Then, the memory contents and the initialization state of the execution program are detected, and the shooting preparation operation is executed. In step S105, the imaging operation of the image sensor is started, and a low-pixel moving image for preview is output. In step S107, the read moving image is displayed on the display 131 provided on the rear surface of the image pickup apparatus, and the photographer visually determines the composition at the time of photographing by viewing the preview image.

  In step S109, it is recognized whether or not a face exists in the preview moving image. If it is recognized that a face exists in the shooting area (“YES” in step S111), the process proceeds from step S111 to step S113, and the focus adjustment mode is set to the face AF mode. Here, the face AF mode refers to an AF mode for focusing on the face in the shooting area.

  On the other hand, if no face is present in the shooting area (“NO” in step S111), the process proceeds from step S111 to step S115, and the focus adjustment mode is set to the multipoint AF mode. Here, the multi-point AF mode refers to, for example, dividing the shooting area by 3 × 5 = 15, performing focus detection in each divided area, inferring the main subject from the focus detection result and the luminance information of the subject, and focusing the region. Refers to the mode to be activated.

  When the AF mode is determined in step S113 or step S115, the focus detection area is determined in step S117. In step S121, it is determined whether or not the photographing preparation switch is turned on. If the photographing preparation switch is not turned on, the process returns to step S105, and the determination of the focus detection area in step S117 is repeatedly executed from the image sensor driving.

  When the photographing preparation switch is turned on in step S121, the process proceeds to step S131, and a focus detection subroutine is executed.

  FIG. 19 is a flowchart of the focus detection subroutine. When the process proceeds from step S121 of the main flow to step S131 of this subroutine, in step S133, the focus detection pixels included in the focus detection area determined in step S117 of the main routine are read. In step S134, a plurality of sections are assigned to the imaging surface of the imaging device 107 so as to include at least two focus detection units 901. The sections are preferably arranged so as not to overlap each other. In addition, sections may be assigned so that all the focus detection units 901 on the imaging surface of the image sensor 107 are arranged in any section, or some focus detection units 901 are not arranged in any section. Sections may be assigned. In step S135, in each of the plurality of sections assigned in step S134, the output signals from the first focus detection pixels in the focus detection unit 901 are combined to obtain a first combined signal. Similarly, in each of the plurality of sections allocated in step S134, the output signal from the second focus detection pixel is synthesized to obtain a second synthesized signal. In step S136, the first combined signal obtained in step S135 is concatenated across a plurality of sections assigned in step S134 to obtain a first concatenated signal. Similarly, the second combined signal obtained in step S135 is concatenated across a plurality of sections assigned in step S134 to obtain a second concatenated signal. These first and second concatenated signals correspond to two image signals for correlation calculation. Specifically, it corresponds to a pair of signals such as AFSIGh (A1) and AFSIGh (B1) or AFSIGv (C3) and AFSIGv (D3) shown in FIG. In step S139, the correlation between the two image signals obtained is calculated, and the relative displacement between the two image signals is calculated. In step S141, the reliability of the correlation calculation result in step S139 is determined. Here, the reliability refers to the degree of coincidence of the signals of the two images. When the degree of coincidence of the signals of the two images is good, the reliability of the focus detection result is generally high. Therefore, when a plurality of focus detection areas are selected, highly reliable information is preferentially used.

  In step S143, the defocus amount is calculated from the above reliable detection result. In step S145, the process returns to step S151 in the main flow of FIG.

  In step S151 of FIG. 18, it is determined whether or not the amount of defocus calculated in step S143 of FIG. If the defocus amount is an allowable value abnormality, it is determined that the in-focus state is out of focus, the focus lens is driven in step S153, and then step S131 to step S151 are repeatedly executed. If it is determined in step S151 that the in-focus state has been reached, in-focus display is performed in step S155, and the process proceeds to step S157.

  In step S157, it is determined whether or not the shooting start switch has been turned on. If the switch has not been turned on, the shooting standby state is maintained in step S157. When the shooting start switch is turned on in step S157, the process proceeds to step S161, and a shooting subroutine is executed.

  FIG. 20 is a flowchart of the photographing subroutine. When the photographing start switch is operated, via step S161, in step S163, the light amount adjusting diaphragm is driven to perform aperture control of the mechanical shutter that defines the exposure time. In step S165, image reading for high-pixel still image shooting, that is, reading of all pixels is performed. In step S167, defective pixel interpolation of the read image signal is performed. That is, the output of the focus detection pixel does not have RGB color information for imaging, and corresponds to a defective pixel in obtaining an image. Therefore, an image signal is generated by interpolation from information on surrounding imaging pixels. .

  In step S169, image processing such as γ correction and edge enhancement of the image is performed. In step S171, the captured image is recorded in the flash memory 133. In step S173, the captured image is displayed on the display 131, and the process returns to the main flow in FIG. 18 in step S175.

  Returning to the main flow of FIG. 18, a series of photographing operations is terminated in step S181.

  As described above, according to the first preferred embodiment of the present invention, outputs of a plurality of focus detection pixels having a pupil division function can be combined and used for focus detection calculation. Therefore, the sampling characteristic and S / N of the focus detection signal can be improved. In addition, since the focus detection pixels are discretely arranged, there are few defects in the imaging pixels, and deterioration of the captured image can be avoided.

  In addition, the AF pixel for obtaining the phase difference detection signal is rectangular, and a signal obtained by synthesizing the outputs of the focus detection pixels in the rectangular area is used as a signal for one AF calculation pixel. Then, by reducing the size of the rectangular area in the direction orthogonal to the pupil division direction relative to the other, it is possible to prevent the AF pixel sampling ability from decreasing in the direction orthogonal to the pupil division direction. Therefore, it is possible to prevent a thin line or high-frequency subject from being captured and to improve focus detection performance.

  Further, the lateral shift detection pixels and the vertical shift detection pixels can be arranged in a checkered pattern at substantially equal intervals and at equal arrangement density. As a result, accurate focus detection can be performed for both a subject having a luminance distribution in the horizontal direction and a subject having a luminance distribution in the vertical direction.

  In the present embodiment, the case where the focus detection pixels are distributed over the entire area of the imaging surface of the imaging device has been described as an example, but the present invention is not limited to this. For example, it is possible to make changes such as not disposing the focus detection pixels in the peripheral area of the image sensor within a range not departing from the scope of the present invention.

(Second Embodiment)
In the first embodiment, a pair of lateral shift detection pixels or a pair of vertical shift detection pixels are assigned to positions of R pixels and B pixels adjacent in an oblique direction. The second embodiment described below is an embodiment in which the focus detection pixels are assigned only to pixels of a single color, that is, R pixels or B pixels. The configuration of the second embodiment will be described with reference to FIGS.

FIG. 21 is a diagram illustrating a focus detection pixel array according to the second embodiment, and corresponds to FIG. 9 according to the first embodiment. In the first embodiment shown in FIG. 9, focus detection pixels S _HA , S _HB , S _VC and S are located at positions of R pixels and B pixels adjacent in the oblique direction in the imaging pixels having the Bayer array. _VD was assigned. In contrast, in the second embodiment shown in FIG. 21, focus detection pixels are assigned only to B pixels in the Bayer array. Specifically, in the upper left block BLK _h (1, 1) and the lower right block BLK _h (2, 2), two B pixels located on the left side of the lowermost row are horizontally divided into pupils. _Are replaced with a set of focus detection pixels S _HA and S _HB .

In the remaining blocks BLKv (1, 2) and BLKv (2, 1), a set of focus detections that perform pupil division in the vertical direction on the two B pixels located on the lower side of the second column from the left. The pixels S _VC and S _VD are replaced.

  Generalizing this arrangement rule, as in the first embodiment, in block BLK (i, j), if i + j is an even number, a focus detection pixel for horizontal pupil division is arranged, and if i + j is an odd number, Focus detection pixels for vertical pupil division are arranged. An area of 2 × 2 = 4 blocks, that is, 20 rows × 20 columns = 400 pixels is a cluster.

FIG. 22 is a diagram for explaining the arrangement rule with the cluster as a unit, and corresponds to FIG. 10 of the first embodiment. In FIG. 22, the upper left cluster composed of 20 rows × 20 columns = 400 pixels is assumed to be CST (u, w) = CST (1, 1). In the cluster CST (1, 1), the B pixel located on the lower left side of each block is replaced with focus detection pixels S _HA and S _HB or S _VC and S _VD .

  In the cluster CST (1, 2) on the right side, the focus detection pixels in the block are arranged at positions shifted upward by two pixels with respect to the cluster CST (1, 1). In the cluster CST (2, 1) adjacent to the first cluster CST (1, 1), the focus detection pixel is arranged in the block in the right direction with respect to the cluster CST (1, 1). Arranged at a position shifted by two pixels. When the above rule is repeatedly applied, the arrangement shown in FIG. 22 is obtained, and the range shown in FIG. 22 becomes a field positioned at the top of the cluster. In the first embodiment shown in FIG. 10, 5 × 5 = 25 clusters are one field, but in the second embodiment, 4 × 4 = 16 clusters are one field.

  FIG. 23 is a diagram for explaining an arrangement rule with the above field as a unit, and corresponds to FIG. 11 of the first embodiment. In FIG. 23, the upper left field composed of 80 rows × 80 columns = 6,400 pixels is assumed to be FLD (q, r) = FLD (1,1). Also in the second embodiment, all the fields FLD (q, r) have the same arrangement as the first field FLD (1, 1). Therefore, when 37 FLDs (1, 1) are arranged in the horizontal direction and 25 in the vertical direction, an imaging area of 3000 columns × 2000 rows = 6 million pixels is configured by 925 fields. However, the 40 columns at the right end are fractional areas where one field could not be constructed, and focus detection pixels are not arranged in this area, but the focus detection pixels are substantially uniformly distributed over the entire imaging area. ing.

  Next, a group of pixels and a signal addition method at the time of focus detection will be described with reference to FIGS. FIG. 12 is a diagram for explaining a pixel grouping method in the case of performing focus detection in the lateral shift direction of the subject image formed by the photographing optical system, and corresponds to FIG. 12 of the first embodiment.

The pixel arrangement shown in FIG. 24 is the same as that described with reference to FIG. 22, but in the focus detection, one block in the horizontal direction and eight blocks in the vertical direction are combined into one section. In the second embodiment, one focus detection area is configured by 24 sections arranged in the horizontal direction. That is, an area of 80 rows × 240 columns = 19, 200 pixels is one focus detection area. This one focus detection area is an AF area. Here, in one section, four pixels S _HA that perform one pupil division in the horizontal direction and four pixels S _HB that perform the other pupil division are included. Therefore, in the second embodiment, the outputs of the four _SHAs are added to form one AF pixel of one image signal (referred to as an A image) for phase difference calculation. Similarly, the outputs of the four _SHBs are added to form a 1AF pixel of the other image signal (referred to as a B image) for phase difference calculation.

FIG. 25 is a diagram for explaining the subject image capturing capability in one section, and corresponds to FIG. 13 of the first embodiment. FIG. 25A shows the section at the left end of FIG. A horizontal line PRJ _h shown at the lower end is a first projection line extending in a second direction orthogonal to the pupil division direction (first direction) of the focus detection pixels S _HA and S _HB. . Vertical line PRJ _v shown at the right end is a second projection axis which extends in the pupil division direction. Here, all the pixels S _HA in one section are added, and S _HB is also added. Therefore, when one section is regarded as one AF pixel, pixels S _HA and S _HB are alternately arranged densely when the light receiving portion included in the one AF pixel is projected onto a projection axis PRJ _h in a direction orthogonal to the pupil division direction. I understand. If the average arrangement pitch of the pixels S _{HA on} the projection axis PRJ _h in the direction orthogonal to the pupil division direction at this time is P1, P1 = PH _h = 2 (unit is a pixel). When expressed by the spatial frequency F1 instead of the pitch, F1 = 0.5 (unit is pixel / pixel). Similarly, the arrangement pitch of the pixels S _HB on the projection axis PRJ _h is also P1 = 2 (unit is pixel), and F1 = 0.5 (unit is pixel / pixel) in the spatial frequency notation.

On the other hand, when projecting the light receiving portions included in 1AF pixel in the pupil division direction in projection axis PRJ _v, the pixel _{S HA} and _{S HB} is seen that aligned sparsely. If the arrangement pitch of the pixels S _{HA on} the projection axis PRJ _{v at} this time is P2, then P2 = PH _v = 20 (the unit is a pixel). When expressed by the spatial frequency F2 instead of the pitch, F2 = 0.05 (unit: pixel / pixel). Similarly, the array pitch of the pixels _{S HB} along the projection PRJ _v also, P2 = 20 (the unit is a pixel), a F2 = 0.05 (the unit is pixel / pixel) of the spatial frequency notation. That is, it can be seen that the sampling characteristics of the subject image of the AF pixel in the second embodiment are substantially equal to those in the first embodiment.

The image capture capability when a thin line subject image is projected onto the AF pixel (one section) described in FIG. 25A will be described with reference to FIG. In FIG. 25B, LINE _v represents a thin vertical line projected on the image sensor 107, and the width thereof is 4 pixels in terms of pixels, and the actual size of the image is 8 μm. At this time, in the section SCT _h (1), the focus detection pixels included in the block BLK (1, 1), the block BLK (3, 1), and the block BLK (5, 1) capture the subject image. That is, also in the second embodiment, an image is captured by at least one pixel S _HA and S _HB in one section, and no capture leakage occurs.

On the other hand, LINE _h in FIG. 25B represents a thin horizontal line of 4 pixels wide projected on the image sensor 107. At this time, the horizontal line LINE _h covers the block BLK (5, 1), but is not captured by the focus detection pixels S _HA and S _HB . However, the section SCT _h (1) is for performing focus detection on a subject having a luminance distribution in the horizontal direction such as a vertical line. Therefore, for an object having a luminance distribution in the vertical direction such as a horizontal line, an image capturing omission due to focus detection pixels may occur.

  Note that the characteristics in detecting the focus in the longitudinal shift direction in the second embodiment are equivalent to those obtained by rotating FIG. 25 by 90 degrees, and thus the description thereof is omitted. Further, the flow described in FIGS. 17 to 20 may also be used for the focus detection operation. In the above description, the focus detection pixels are assigned to the B pixels, but may be assigned to the R pixels. Further, the arrangement of a set of focus detection pixels is not limited to the embodiment. For example, in FIG. 21, a pair of focus detection pixels in the lateral shift direction are arranged apart from each other in the horizontal direction, but may be arranged apart from each other in the vertical direction.

  According to the second embodiment described above, since the focus detection pixels are assigned to single color pixels, the defective pixel interpolation algorithm at the time of output image generation is simplified. In addition, image deterioration and false color in a specific color are reduced.

(Third embodiment)
The focus detection pixels used in the first embodiment and the second embodiment are a set of two, and for one pupil region divided into two, one pixel receives a light beam passing through one pupil, The other pixel received the light beam passing through the other pupil. On the other hand, a third embodiment described below shows an embodiment using an imaging device that acquires a luminous flux of a pupil region divided into two by one pixel and outputs the signal.

  Hereinafter, the third embodiment will be described with reference to FIGS. 26 and 27.

FIG. 26 is a diagram illustrating a focus detection pixel array according to the third embodiment, and corresponds to FIG. 9 according to the first embodiment. In the first embodiment shown in FIG. 9, focus detection pixels S _HA , S _HB , S _VC and S are located at positions of R pixels and B pixels adjacent in the oblique direction in the imaging pixels having the Bayer array. _VD was assigned. On the other hand, in the third embodiment shown in FIG. 26, a focus detection pixel is assigned to one R pixel in each block of 10 × 10 = 100 pixels. Specifically, in the upper left block BLK _h (1, 1) and the lower right block BLK _h (2, 2), one R pixel at the lowermost end of the left end column is horizontally pupild. It is replaced with one focus detection pixel _SHAB to be divided. Here, the technique disclosed in Japanese Patent Application Laid-Open No. 2003-156667 by the present applicant may be used for the focus detection pixel S _HAB . That is, as in the imaging device disclosed in FIG. 2 of this publication, the photoelectric conversion element behind the on-chip microlens is divided into multiple parts to divide the pupil of the photographing optical system, and the luminous flux from each divided pupil region is It is acquired independently and output as an image signal. Therefore, one set of signals for phase difference detection is obtained with one pixel.

In the remaining blocks BLKv (1, 2) and BLKv (2, 1), one focus detection pixel S _VAB that performs pupil division in the vertical direction on one R pixel at the lowermost end of the leftmost column. Replace with.

  Generalizing this arrangement rule, as in the first embodiment, in block BLK (i, j), if i + j is an even number, a focus detection pixel for horizontal pupil division is arranged, and if i + j is an odd number, Focus detection pixels for vertical pupil division are arranged. An area of 2 × 2 = 4 blocks, that is, 20 rows × 20 columns = 400 pixels is a cluster.

  FIG. 27 is a diagram for explaining an arrangement rule in which a plurality of clusters are collected with the above cluster as a unit, and corresponds to FIG. 10 of the first embodiment. The entire area shown in FIG. 27 represents one field that is higher in the cluster, but the arrangement rule in the field is the same as in the first embodiment.

  The field arrangement, focus detection characteristics, and focus detection flow in the entire imaging region in the third embodiment are the same as those shown in FIGS. .

  According to the third embodiment described above, since the ratio of the number of pixels allocated to the focus detection pixels is reduced, deterioration of the output image and false colors are further reduced. In addition, the defective pixel interpolation algorithm when generating the output image is simplified.

(Fourth embodiment)
In the first to third embodiments, the lateral deviation detection pixels and the vertical deviation detection pixels are arranged with the same arrangement density. However, in the fourth embodiment described below, only one pixel is arranged. Embodiment. The configuration of the fourth embodiment will be described with reference to FIGS.

FIG. 28 is a diagram illustrating a focus detection pixel array according to the fourth embodiment, and corresponds to FIG. 12 according to the first embodiment. In the fourth embodiment, the block that is the minimum unit of the pixel array is configured by 10 rows × 10 columns = 100 pixels as in the first embodiment. However, the focus detection pixels included in the fourth embodiment are only the pixels shown in FIG. 6, that is, the pixels S _HA and S _HB that divide the pupil of the photographing optical system in the horizontal direction. One section for focus detection is composed of 2 × 5 = 10 blocks, that is, 50 rows × 20 columns = 1000 pixels. In each section, the focus detection pixel pairs are arranged in a V shape as illustrated. However, in each block BLK (i, j), the arrangement positions of the focus detection pixel pairs in the vertical direction are different between an odd-numbered block group and an even-numbered block group.

FIG. 29 is a diagram for explaining the subject image capturing capability in one section, and corresponds to FIG. 13 of the first embodiment. FIG. 29A shows the section at the left end of FIG. The horizontal line PRJ _h shown at the lower end is shown at the right end of the first projection axis extending in the second direction orthogonal to the pupil division direction (first direction) of the focus detection pixels S _HA and S _HB. vertical line PRJ _v is the second projection axis which extends in the pupil division direction. In the fourth embodiment, the output of the pixel SH _A in one section are added all the output of the S _HB are also added. Accordingly, when one section is regarded as one AF pixel, pixels SH _A and SH _B are alternately arranged densely when the light receiving portion included in the one AF pixel is projected onto a projection axis PRJ _h in a direction orthogonal to the pupil division direction. I understand. When the arrangement pitch of the pixels SH _{A on} the projection axis PRJ _h in the direction orthogonal to the pupil division direction at this time is P1, P1 = PH _h = 2 (unit is a pixel). When expressed by the spatial frequency F1 instead of the pitch, F1 = 0.5 (unit is pixel / pixel). Similarly, the arrangement pitch of the pixels S _HB on the projection axis PRJ _h is also P1 = 2 (unit is pixel), and F1 = 0.5 (unit is pixel / pixel) in the spatial frequency notation.

On the other hand, when projecting the light receiving portions included in one AF pixel projection axis PRJ _v in the pupil division direction, the pixels S _HA and S _HB is seen that arranged in sparsely, and unequal. At this time, the arrangement pitch of the pixels S _{HA on} the projection axis PRJ _v has two values, the larger pitch is PH _v1 = 6, the smaller pitch is PH _v2 = 4, and the average value is P2 = 5 (both units) Is a pixel). When expressed by the average spatial frequency F2 instead of the pitch, F2 = 0.2 (unit is pixel / pixel). The average arrangement pitch of the pixels _{S HB} at Similarly projection axis PRJ _v also, P2 = 5 (the unit is a pixel), a F2 = 0.2 (the unit is a pixel / pixel) the average spatial frequency notation.

  That is, in the AF pixel according to the fourth embodiment, the dispersion characteristics before the grouping are different in the arrangement characteristics in the pupil division direction and the direction orthogonal to the pupil division direction, but the group shape at the time of grouping is rectangular. The desired sampling characteristics are obtained. Specifically, the maximum dimension L1 in the direction orthogonal to the pupil division direction of one section is 20 pixels, and the maximum dimension L2 in the pupil division direction is 50 pixels. That is, by setting the section size to L1 <L2, the sampling frequency F1 in the direction orthogonal to the pupil division direction is set to a high frequency (fine), and the sampling frequency F2 in the pupil division direction is set to a low frequency (sparse).

FIG. 29B illustrates the image capturing capability when a thin line subject image is projected onto the AF pixel (one section) described with reference to FIG. In FIG. 29B, LINE _v represents a thin vertical line projected on the image sensor 107, the width of which is 4 pixels in terms of pixel, and the actual size of the image is 8 μm. At this time, in the section SCT _h (1), the focus detection pixels included in the block BLK (3, 1) and the block BLK (4, 1) capture the subject image.

Further, LINE _C in FIG. 29 (b) vertical lines LINE _v Ta is inclined vertical line rotated 15 degrees counterclockwise. This inclined vertical line is captured by the focus detection pixels included in the block BLK (4, 2). On the other hand, in the fourth embodiment, since no vertical shift detection pixel is provided, focus detection is impossible for the horizontal line.

  FIG. 30 is a pixel arrangement diagram in the entire region of the image sensor 107 and corresponds to FIG. 11 of the first embodiment. In the fourth embodiment, since the section described with reference to FIG. 28 also corresponds to a field, as shown in FIG. 30, the imaging region is configured by 40 × 150 = 6000 fields. The focus detection in the lateral shift direction is possible over the entire imaging region.

  According to the fourth embodiment described above, the arrangement rule of the focus detection pixels is simplified, so that the memory area for storing the arrangement rule can be saved, and the device can be manufactured at low cost. Also, the algorithm for complementing defective pixels is simplified, the image processing speed is improved, and light focus adjustment can be taken.

  In the first to fourth embodiments described above, the embodiments of the digital still camera have been described. However, the present invention is not limited to this. The image pickup apparatus of the present invention can be applied not only to a digital still camera but also to a camcorder (movie camera) that performs moving image shooting, various inspection cameras, a surveillance camera, an endoscope camera, a robot camera, and the like. Further, in the first to fourth embodiments described above, the synthesis includes addition and averaging.

  The arrangement, numerical values, and the like of the components described in the first to fourth embodiments described above are illustrative, and are not intended to limit the scope of the present invention only to them.

  The present invention provides a focus adjustment operation of an imaging apparatus such as an electronic camera equipped with an imaging element, and is particularly useful for a digital still camera and a movie camera.

1 is a configuration diagram of an imaging apparatus according to a preferred embodiment of the present invention. It is a circuit diagram of an image sensor according to a preferred embodiment of the present invention. It is a pixel sectional view of the image sensor concerning a suitable embodiment of the present invention. 3 is a drive timing chart of an image sensor according to a preferred embodiment of the present invention. It is the top view and sectional drawing of the pixel for an imaging of the image pick-up element which concerns on suitable embodiment of this invention. 2A and 2B are a plan view and a cross-sectional view of a focus detection pixel of an image sensor according to a preferred embodiment of the present invention. It is the top view and sectional view of other focus detection pixels of an image sensor according to a preferred embodiment of the present invention. It is a conceptual diagram explaining the focus detection which concerns on suitable embodiment of this invention. FIG. 2 is a pixel array explanatory diagram of a minimum unit of the image sensor according to the preferred first embodiment of the present invention. It is a pixel arrangement explanatory drawing of the upper unit of the image sensor according to the preferred first embodiment of the present invention. It is a pixel arrangement explanatory view in the whole area of the image sensor according to the preferred first embodiment of the present invention. It is a pixel grouping method explanatory view at the time of lateral shift focus detection according to a preferred first embodiment of the present invention. It is an image sampling characteristic explanatory view at the time of lateral shift focus detection according to a preferred first embodiment of the present invention. It is a pixel grouping method explanatory view at the time of longitudinal shift focus detection according to a preferred first embodiment of the present invention. It is image sampling characteristics explanatory drawing at the time of longitudinal shift focus detection concerning a suitable 1st embodiment of the present invention. It is a conceptual diagram explaining the pupil division | segmentation condition of the image pick-up element which concerns on suitable 1st Embodiment of this invention. It is a focus detection area explanatory drawing concerning a suitable 1st embodiment of the present invention. It is a main control flow figure concerning a suitable embodiment of the present invention. It is a focus detection subroutine flow chart concerning a preferred embodiment of the present invention. It is an imaging | photography subroutine flowchart which concerns on suitable embodiment of this invention. It is pixel array explanatory drawing of the minimum unit of the image pick-up element which concerns on suitable 2nd Embodiment of this invention. It is pixel arrangement explanatory drawing of the high-order unit of the image pick-up element which concerns on suitable 2nd Embodiment of this invention. It is pixel arrangement explanatory drawing in the whole area | region of the image pick-up element based on suitable 2nd Embodiment of this invention. It is a pixel grouping method explanatory view at the time of lateral shift focus detection according to a preferred second embodiment of the present invention. It is image sampling characteristics explanatory drawing at the time of a lateral shift focus detection concerning a suitable 2nd embodiment of the present invention. It is pixel arrangement explanatory drawing of the minimum unit of the image pick-up element concerning the suitable 3rd Embodiment of this invention. It is pixel arrangement explanatory drawing of the upper unit of the image pick-up element concerning the suitable 3rd Embodiment of this invention. It is a pixel grouping method explanatory view at the time of focus detection according to a preferred fourth embodiment of the present invention. It is image sampling characteristics explanatory drawing at the time of focus detection concerning a suitable 4th embodiment of the present invention. It is pixel array explanatory drawing in the whole area | region of the image pick-up element based on suitable 4th Embodiment of this invention.

Explanation of symbols

107 Image sensor 901 Focus detection unit 901a First focus detection pixel 901b Second focus detection pixel 902 Composition unit 903 Connection unit 904 Calculation unit

Claims (11)

An imaging device having a plurality of focus detection units each composed of a first focus detection pixel and a second focus detection pixel which are divided into pupils;
Processing for obtaining a first synthesized signal by synthesizing output signals from the first focus detection pixels in each of a plurality of sections respectively assigned to the image sensor so as to include a plurality of the focus detection units; Combining means for combining the output signals from the second focus detection pixels to obtain a second combined signal;
A concatenation that performs processing for concatenating the first composite signal to obtain a first concatenated signal and processing for concatenating the second composite signal to obtain a second concatenated signal over the plurality of sections. Means,
An arithmetic means for calculating a defocus amount of the imaging optical system based on the first connection signal and the second connection signal;
An imaging apparatus comprising:   The imaging apparatus according to claim 1, wherein the imaging element includes a plurality of imaging pixels for photoelectrically converting a subject image formed by the imaging optical system. Of the plurality of focus detection units, the first focus detection unit is configured such that the first focus detection pixels and the second focus detection pixels are pupil-divided in a first direction, and The first section in the first section and the second direction perpendicular to the first direction are arranged at equal intervals in the first section,
3. The imaging according to claim 1, wherein an interval of the first focus detection unit in the first direction is smaller than an interval of the first focus detection unit in the second direction. apparatus.   The imaging apparatus according to claim 3, wherein a maximum dimension of the first section in the first direction is smaller than a maximum dimension of the first section in the second direction. Of the plurality of focus detection units, the second focus detection unit is configured such that the first focus detection pixels and the second focus detection pixels are pupil-divided in the second direction and the plurality of sections. Are arranged at equal intervals in the first direction and the second direction in the second section,
5. The imaging according to claim 3, wherein an interval of the second focus detection unit in the second direction is smaller than an interval of the second focus detection unit in the first direction. 6. apparatus.   The imaging device according to claim 5, wherein a maximum dimension of the second section in the second direction is smaller than a maximum dimension of the second section in the first direction. The first section is composed of a plurality of square regions,
5. The imaging apparatus according to claim 1, wherein one first focus detection unit is disposed in each of the plurality of square regions. The second section is composed of a plurality of square regions,
The imaging device according to claim 5, wherein one second focus detection unit is arranged in each of the plurality of square regions.   A square region in which the first focus detection unit according to claim 7 is arranged, and a square region in which the second focus detection unit according to claim 8 is arranged include the first direction and the second region. An imaging device, wherein the imaging devices are alternately arranged in the direction of.   The imaging apparatus according to claim 9, wherein an arrangement density of the first focus detection units is equal to an arrangement density of the second focus detection units. A method for controlling an imaging apparatus including an imaging element having a plurality of focus detection units each including a first focus detection pixel and a second focus detection pixel that are divided into pupils,
Assigning a plurality of sections including a plurality of the focus detection units to the image sensor;
Synthesizing output signals from the first focus detection pixels in each of the plurality of sections to obtain a first synthesized signal;
Synthesizing output signals from the second focus detection pixels in each of the plurality of sections to obtain a second synthesized signal;
Concatenating the first combined signal across the plurality of sections to obtain a first concatenated signal;
Concatenating the second composite signal over the plurality of sections to obtain a second concatenated signal;
Calculating a defocus amount of the imaging optical system based on the first connection signal and the second connection signal;
It is characterized by including.

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